PROJECT SUMMARY: Chronic obstructive pulmonary disease results from a complex interplay of environmental factors, host immune responses, and microbial factors. The bacterium Haemophilus influenzae colonizes the human respiratory tract and is an important pathogen associated with COPD. The overall goal of this study is to identify H. influenzae factors that contribute to the pathogenesis of COPD. The underlying principles exploited in this proposal are that H. influenzae are genetically highly variable and that natural selection preserves necessary genes among specific populations of bacteria. In Specific Aim 1 the prevalence of known H. influenzae virulence genes will be described among H. influenzae strains isolated form patients with COPD and from adults without COPD. In Specific Aim 2 additional genes that segregate differentially among H. influenzae isolated from patients with COPD and from adults without COPD will be identified. This gene discovery effort will utilize subtractive genomic hybridization to identify H. influenzae DNA fragments that correspond to genes present in a representative COPD H. influenzae strain but absent in a representative commensal strain. The prevalence of the resultant DNA fragments among COPD and non-COPD H. influenzae strains will be assessed using a bacterial genomic microarray technique. In addition, the corresponding genes of the COPD-associated DNA fragments will be defined and mapped on the H. influenzae chromosome, and the extent of the deletion in flanking regions of the commensal strain assessed. In Specific Aim 3, the co-occurrence of the potential COPD-associated virulence genes among COPD strains will be described and the relative contribution of each gene to the "COPD pathotype" will be determined using a classification tree analysis. In Specific Aim 4, the expression of immune mediators by human epithelial cells in response to H. influenzae of the "COPD pathotypes" will be measured using ELISA. PROJECT RELEVANCE: The results of this project will identify H. influenzae genes that are associated with COPD will describe their role in stimulating immune responses by human epithelial cells. These results will lead to a better understanding of the H. influenzae virulence pathways associated with COPD and lead to novel new strategies for prevention and management of COPD.